Preparation And Electric Properties Of BST Ferroelectric Thin Film Infrared Detector Arrays

Ferroelectric thin films and ferroelectric integrated devices are the current research hotspot in material science and microelectronics. In this paper, Ba0.80Sr0.20TiO3(BST) ferroelectric thin films were prepared by RF magnetic sputtering method. The structure and photolithography mask layouts of detector arrays were designed, and the microfabrication processes of BST thin films and metal electrodes were also investigated.8×8and16×16elements detector arrays were fabricated, electrical properties of8×8elements detector arrays were characterized. The results are listed as follows:(1) The effect of working pressure, ratio of O2/Ar, and substrate temperature on the formation of BST thin films were studied, the optimized deposition parameter conditions were obtained.800nm BST ferroelectric thin films were deposited by RF magnetic sputtering method using optimized process parameters. Under30V test voltage at room temperature, the remnant polarization2Pr is6.47μC/cm2for the800nm thin films. The leakage current is4.22×10-10A at5V voltage, and the dielectric constant, dielectric loss of the films are428,0.007at200KHz, respectively.(2) Using photolithography-lift off process, Pt/Ti bottom electrode, Au top electrode and Ni/Cr absorption layer were patterned. By photolithography-wet chemical etch method, BST thin film micrographics were also fabricated successfully. The optimized lithography processes of ENPI202and AZ5214E photoresist were discussed in detail. An improved etchant with volume ratio of HF(40wt%):HNO3(65.68wt%):H2O2(30wt%)=1:20:50was developed for etching BST thin films in30℃thermostatic waterbath. The etching time is about18s for800nm films and the etch rate is about44.44nm/s. The experimental results show that the surfaces are clean and the edges of etched films are sharp and smooth. After post-annealing treatment to etched films at600℃for30min in air atmosphere, the degradation caused by the etch process can be recovered.(3) The structure of ferroelectric thin film infrared detector arrays was designed, and lithography mask layouts of each layer were designed by using L-edit software.8×8and16×16elements detector arrays were fabricated. The ferroelectric property, dielectric property and leakage current performance of the8×8elements detector arrays were measured. Under 30V test voltage, the remnant polarization2Pr of the arrays is1.83μC/cm". The leakage current is9.02×10-6A at5V voltage, and the dielectric constant and dielectric loss of the arrays are276,0.013at200KHz, respectively.